Microstructure and residual stress in hydrogenated amorphous silicon (a-Si:H) layers

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dc.contributor.advisorBritton, David Ten_ZA
dc.contributor.advisorHärting, Margiten_ZA
dc.contributor.authorRamukosi, Fhatuwani Lawrenceen_ZA
dc.date.accessioned2014-08-13T20:12:15Z
dc.date.available2014-08-13T20:12:15Z
dc.date.issued2006en_ZA
dc.descriptionIncludes bibliographical references.en_ZA
dc.description.abstractHydrogenated amorphous silicon (a-Si:H) is known to be highly disordered. The disorder introduces a high amount of defects in the network, such as bond length and angle deviation, non-coordinated bonds or voids. In this work the microstructural characterization and a new approach for strain determination in hydrogenated amorphous silicon in the layers is determined by synchrotron diffraction. The a-Si:H layers were deposited by hotwire chemical vapour deposition (HW -CVD) on a glass substrate at a growth temperature of 300°C and 500°C, respectively. The microstructural state from the diffraction phase has been experimentally determined using the pair correlation function, calculated using Fourier transformation of the scattered intensity. Indication of the residual stress in the layers was obtained using the conventional sin²ψ method, normally used and especially developed for polycrystalline materials, but here applied to an amorphous structure. It is found that residual stress and microstructure of the layers are correlated The pair distribution function (PDF) of the short range order reveals a significant shift in the nearest neighbour distance of Si-Si pairs leading to bond strain in the layers. The PDF reveals that the short-range bonding of a Si:H is tetrahedral but it does not give much information about the intermediate region which relates to the structural topology. We observed a deviation in the nearest-neighbour and the second nearest-neighbour separation, independent of the growth temperature. The observed strain curves deviate from the linear prediction of the conventional sin²ψ method. The layers were found to be generally under compressive stress, with strong gradients dominant in the interface region of the sample, and the resulting stress is highly dependent on the details of the deposition process.en_ZA
dc.identifier.apacitationRamukosi, F. L. (2006). <i>Microstructure and residual stress in hydrogenated amorphous silicon (a-Si:H) layers</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Physics. Retrieved from http://hdl.handle.net/11427/6548en_ZA
dc.identifier.chicagocitationRamukosi, Fhatuwani Lawrence. <i>"Microstructure and residual stress in hydrogenated amorphous silicon (a-Si:H) layers."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Physics, 2006. http://hdl.handle.net/11427/6548en_ZA
dc.identifier.citationRamukosi, F. 2006. Microstructure and residual stress in hydrogenated amorphous silicon (a-Si:H) layers. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Ramukosi, Fhatuwani Lawrence AB - Hydrogenated amorphous silicon (a-Si:H) is known to be highly disordered. The disorder introduces a high amount of defects in the network, such as bond length and angle deviation, non-coordinated bonds or voids. In this work the microstructural characterization and a new approach for strain determination in hydrogenated amorphous silicon in the layers is determined by synchrotron diffraction. The a-Si:H layers were deposited by hotwire chemical vapour deposition (HW -CVD) on a glass substrate at a growth temperature of 300°C and 500°C, respectively. The microstructural state from the diffraction phase has been experimentally determined using the pair correlation function, calculated using Fourier transformation of the scattered intensity. Indication of the residual stress in the layers was obtained using the conventional sin²ψ method, normally used and especially developed for polycrystalline materials, but here applied to an amorphous structure. It is found that residual stress and microstructure of the layers are correlated The pair distribution function (PDF) of the short range order reveals a significant shift in the nearest neighbour distance of Si-Si pairs leading to bond strain in the layers. The PDF reveals that the short-range bonding of a Si:H is tetrahedral but it does not give much information about the intermediate region which relates to the structural topology. We observed a deviation in the nearest-neighbour and the second nearest-neighbour separation, independent of the growth temperature. The observed strain curves deviate from the linear prediction of the conventional sin²ψ method. The layers were found to be generally under compressive stress, with strong gradients dominant in the interface region of the sample, and the resulting stress is highly dependent on the details of the deposition process. DA - 2006 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2006 T1 - Microstructure and residual stress in hydrogenated amorphous silicon (a-Si:H) layers TI - Microstructure and residual stress in hydrogenated amorphous silicon (a-Si:H) layers UR - http://hdl.handle.net/11427/6548 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/6548
dc.identifier.vancouvercitationRamukosi FL. Microstructure and residual stress in hydrogenated amorphous silicon (a-Si:H) layers. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Physics, 2006 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/6548en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Physicsen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherPhysicsen_ZA
dc.titleMicrostructure and residual stress in hydrogenated amorphous silicon (a-Si:H) layersen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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